Electrically variable transmission having two planetary gear sets with one stationary fixed interconnection

ABSTRACT

The electrically variable transmission family of the present invention provides low-content, low-cost electrically variable transmission mechanisms including first and second differential gear sets, a battery, two electric machines serving interchangeably as motors or generators, and two or three selectable torque-transfer devices. The selectable torque transfer devices are engaged singly or in pairs to yield an EVT with a continuously variable range of speeds (including reverse) and at least one mechanically fixed forward speed ratio. The torque transfer devices and the first and second motor/generators are operable to provide five operating modes in the electrically variable transmission, including battery reverse mode, EVT reverse mode, reverse and forward launch modes, continuously variable transmission range mode, and fixed ratio mode.

TECHNICAL FIELD

The present invention relates to electrically variable transmissionswith selective operation both in power-split variable speed ratio rangesand in fixed speed ratios, and having two planetary gear sets, twomotor/generators and at least two torque transmitting mechanisms.

BACKGROUND OF THE INVENTION

Internal combustion engines, particularly those of the reciprocatingpiston type, currently propel most vehicles. Such engines are relativelyefficient, compact, lightweight, and inexpensive mechanisms by which toconvert highly concentrated energy in the form of fuel into usefulmechanical power. A novel transmission system, which can be used withinternal combustion engines and which can reduce fuel consumption andthe emissions of pollutants, may be of great benefit to the public.

The wide variation in the demands that vehicles typically place oninternal combustion engines increases fuel consumption and emissionsbeyond the ideal case for such engines. Typically, a vehicle ispropelled by such an engine, which is started from a cold state by asmall electric motor and relatively small electric storage batteries,then quickly placed under the loads from propulsion and accessoryequipment. Such an engine is also operated through a wide range ofspeeds and a wide range of loads and typically at an average ofapproximately a fifth of its maximum power output.

A vehicle transmission typically delivers mechanical power from anengine to the remainder of a drive system, such as fixed final drivegearing, axles and wheels. A typical mechanical transmission allows somefreedom in engine operation, usually through alternate selection of fiveor six different drive ratios, a neutral selection that allows theengine to operate accessories with the vehicle stationary, and clutchesor a torque converter for smooth transitions between driving ratios andto start the vehicle from rest with the engine turning. Transmissiongear selection typically allows power from the engine to be delivered tothe rest of the drive system with a ratio of torque multiplication andspeed reduction, with a ratio of torque reduction and speedmultiplication known as overdrive, or with a reverse ratio.

An electric generator can transform mechanical power from the engineinto electrical power, and an electric motor can transform that electricpower back into mechanical power at different torques and speeds for theremainder of the vehicle drive system. This arrangement allows acontinuous variation in the ratio of torque and speed between engine andthe remainder of the drive system, within the limits of the electricmachinery. An electric storage battery used as a source of power forpropulsion may be added to this arrangement, forming a series hybridelectric drive system.

The series hybrid system allows the engine to operate with someindependence from the torque, speed and power required to propel avehicle, so the engine may be controlled for improved emissions andefficiency. This system allows the electric machine attached to theengine to act as a motor to start the engine. This system also allowsthe electric machine attached to the remainder of the drive train to actas a generator, recovering energy from slowing the vehicle into thebattery by regenerative braking. A series electric drive suffers fromthe weight and cost of sufficient electric machinery to transform all ofthe engine power from mechanical to electrical in the generator and fromelectrical to mechanical in the drive motor, and from the useful energylost in these conversions.

A power-split transmission can use what is commonly understood to be“differential gearing” to achieve a continuously variable torque andspeed ratio between input and output. An electrically variabletransmission can use differential gearing to send a fraction of itstransmitted power through a pair of electric motor/generators. Theremainder of its power flows through another, parallel path that is allmechanical and direct, of fixed ratio, or alternatively selectable.

One form of differential gearing, as is well known to those skilled inthis art, may constitute a planetary gear set. Planetary gearing isusually the preferred embodiment employed in differentially gearedinventions, with the advantages of compactness and different torque andspeed ratios among all members of the planetary gear set. However, it ispossible to construct this invention without planetary gears, as byusing bevel gears or other gears in an arrangement where the rotationalspeed of at least one element of a gear set is always a weighted averageof speeds of two other elements.

A hybrid electric vehicle transmission system also includes one or moreelectric energy storage devices. The typical device is a chemicalelectric storage battery, but capacitive or mechanical devices, such asan electrically driven flywheel, may also be included. Electric energystorage allows the mechanical output power from the transmission systemto the vehicle to vary from the mechanical input power from the engineto the transmission system. The battery or other device also allows forengine starting with the transmission system and for regenerativevehicle braking.

An electrically variable transmission in a vehicle can simply transmitmechanical power from an engine input to a final drive output. To do so,the electric power produced by one motor/generator balances theelectrical losses and the electric power consumed by the othermotor/generator. By using the above-referenced electrical storagebattery, the electric power generated by one motor/generator can begreater than or less than the electric power consumed by the other.Electric power from the battery can sometimes allow bothmotor/generators to act as motors, especially to assist the engine withvehicle acceleration. Both motors can sometimes act as generators torecharge the battery, especially in regenerative vehicle braking.

A successful substitute for the series hybrid transmission is thetwo-range, input-split and compound-split electrically variabletransmission now produced for transit buses, as disclosed in U.S. Pat.No. 5,931,757, issued Aug. 3, 1999, to Michael Roland Schmidt, commonlyassigned with the present application, and hereby incorporated byreference in its entirety. Such a transmission utilizes an input meansto receive power from the vehicle engine and a power output means todeliver power to drive the vehicle. First and second motor/generatorsare connected to an energy storage device, such as a battery, so thatthe energy storage device can accept power from, and supply power to,the first and second motor/generators. A control unit regulates powerflow among the energy storage device and the motor/generators as well asbetween the first and second motor/generators.

Operation in first or second variable-speed-ratio modes of operation maybe selectively achieved by using clutches in the nature of first andsecond torque transfer devices. In the first mode, an input-power-splitspeed ratio range is formed by the application of the first clutch, andthe output speed of the transmission is proportional to the speed of onemotor/generator. In the second mode, a compound-power-split speed ratiorange is formed by the application of the second clutch, and the outputspeed of the transmission is not proportional to the speeds of either ofthe motor/generators, but is an algebraic linear combination of thespeeds of the two motor/generators. Operation at a fixed transmissionspeed ratio may be selectively achieved by the application of both ofthe clutches. Operation of the transmission in a neutral mode may beselectively achieved by releasing both clutches, decoupling the engineand both electric motor/generators from the transmission output. Thetransmission incorporates at least one mechanical point in its firstmode of operation and at least two mechanical points in its second modeof operation.

U.S. Pat. No. 6,527,658, issued Mar. 4, 2003 to Holmes et al, commonlyassigned with the present application, and hereby incorporated byreference in its entirety, discloses an electrically variabletransmission utilizing two planetary gear sets, two motor/generators andtwo clutches to provide input split, compound split, neutral and reversemodes of operation. Both planetary gear sets may be simple, or one maybe individually compounded. An electrical control member regulates powerflow among an energy storage device and the two motor/generators. Thistransmission provides two ranges or modes of electrically variabletransmission (EVT) operation, selectively providing an input-power-splitspeed ratio range and a compound-power-split speed ratio range. Onefixed speed ratio can also be selectively achieved.

SUMMARY OF THE INVENTION

The present invention provides a family of electrically variabletransmissions offering several advantages over conventional automatictransmissions for use in hybrid vehicles, including improved vehicleacceleration performance, improved fuel economy via regenerative brakingand electric-only idling and launch, and an attractive marketingfeature. An object of the invention is to provide the best possibleenergy efficiency and emissions for a given engine. In addition, optimalperformance, capacity, package size, and ratio coverage for thetransmission are sought.

The electrically-variable transmission family of the present inventionprovides low-content, low-cost electrically variable transmissionmechanisms including first and second differential gear sets, a battery,two electric machines serving interchangeably as motors or generators,and at least two selectable torque-transfer devices (two or threeclutches). Preferably, the differential gear sets are planetary gearsets, but other gear arrangements may be implemented, such as bevelgears or differential gearing to an offset axis.

In this description, the first and second planetary gear sets may becounted left to right or right to left.

Each of the planetary gear sets has three members. The first, second orthird member of each planetary gear set can be any one of a sun gear,ring gear or carrier, or alternatively a pinion.

Each carrier can be either a single-pinion carrier (simple) or adouble-pinion carrier (compound).

The input shaft is not continuously connected with any member of theplanetary gear sets but is selectively connectable with at least onemember of the planetary gear sets through at least one of thetorque-transmitting mechanisms (torque transfer devices). The outputshaft is continuously connected with at least one member of theplanetary gear sets.

A fixed interconnection continuously connects the stationary member to afirst member of the first planetary gear set and a first member of thesecond planetary gear set.

A first torque transfer device selectively connects the input shaft witha member of the first planetary gear set.

A second torque transfer device selectively connects the input shaftwith a member of the first or second planetary gear set.

An optional third torque transfer device selectively connects a memberof the second planetary gear set to the input shaft or to a member ofthe first planetary gear set.

The first motor/generator is mounted to the transmission case (orground) and is continuously connected to a member of the first planetarygear set.

The second motor/generator is mounted to the transmission case and iscontinuously connected to a member of the second planetary gear set.

The two or three selectable torque transfer devices are engaged singlyor in combinations of two to yield an EVT with a continuously variablerange of speeds (including reverse)-and at least one mechanically fixedforward speed ratio. A “fixed speed ratio” is an operating condition inwhich the mechanical power input to the transmission is transmittedmechanically to the output, and no power flow (i.e. almost zero) ispresent in the motor/generators. An electrically variable transmissionthat may selectively achieve several fixed speed ratios for operationnear full engine power can be smaller and lighter for a given maximumcapacity. Fixed ratio operation may also result in lower fuelconsumption when operating under conditions where engine speed canapproach its optimum without using the motor/generators. A variety offixed speed ratios and variable ratio spreads can be realized bysuitably selecting the tooth ratios of the planetary gear sets.

Each embodiment of the electrically variable transmission familydisclosed has an architecture in which neither the transmission inputnor output is directly connected to a motor/generator. This allows for areduction in the size and cost of the electric motor/generators requiredto achieve the desired vehicle performance.

The first, second and optional third torque transfer devices and thefirst and second motor/generators are operable to provide five operatingmodes in the electrically variable transmission, including batteryreverse mode, EVT reverse mode, reverse and forward launch modes,continuously variable transmission range mode, and fixed ratio mode.

The above features and advantages, and other features and advantages ofthe present invention are readily apparent from the following detaileddescription of the best modes for carrying out the invention when takenin connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 a is a schematic representation of a powertrain including anelectrically variable transmission incorporating a family member of thepresent invention;

FIG. 1 b is an operating mode table and fixed ratio mode table depictingsome of the operating characteristics of the powertrain shown in FIG. 1a;

FIG. 2 a is a schematic representation of a powertrain having anelectrically variable transmission incorporating another family memberof the present invention;

FIG. 2 b is an operating mode table and fixed ratio mode table depictingsome of the operating characteristics of the powertrain shown in FIG. 2a;

FIG. 3 a is a schematic representation of a powertrain having anelectrically variable transmission incorporating another family memberof the present invention;

FIG. 3 b is an operating mode table and fixed ratio mode table depictingsome of the operating characteristics of the powertrain shown in FIG. 3a;

FIG. 4 a is a schematic representation of a powertrain having anelectrically variable transmission incorporating another family memberof the present invention;

FIG. 4 b is an operating mode table and fixed ratio mode table depictingsome of the operating characteristics of the powertrain shown in FIG. 4a;

FIG. 5 a is a schematic representation of a powertrain having anelectrically variable transmission incorporating another family memberof the present invention;

FIG. 5 b is an operating mode table and fixed ratio mode table depictingsome of the operating characteristics of the powertrain shown in FIG. 5a;

FIG. 6 a is a schematic representation of a powertrain having anelectrically variable transmission incorporating another family memberof the present invention;

FIG. 6 b is an operating mode table and fixed ratio mode table depictingsome of the operating characteristics of the powertrain shown in FIG. 6a;

FIG. 7 a is a schematic representation of a powertrain having anelectrically variable transmission incorporating another family memberof the present invention;

FIG. 7 b is an operating mode table and fixed ratio mode table depictingsome of the operating characteristics of the powertrain shown in FIG. 7a;

FIG. 8 a is a schematic representation of a powertrain having anelectrically variable transmission incorporating another family memberof the present invention;

FIG. 8 b is an operating mode table and fixed ratio mode table depictingsome of the operating characteristics of the powertrain shown in FIG. 8a;

FIG. 9 a is a schematic representation of a powertrain having anelectrically variable transmission incorporating another family memberof the present invention; and

FIG. 9 b is an operating mode table and fixed ratio mode table depictingsome of the operating characteristics of the powertrain shown in FIG. 9a.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to FIG. 1 a, a powertrain 10 is shown, including anengine 12 connected to one preferred embodiment of the improvedelectrically variable transmission (EVT), designated generally by thenumeral 14. Transmission 14 is designed to receive at least a portion ofits driving power from the engine 12. As shown, the engine 12 has anoutput shaft that serves as the input member 17 of the transmission 14.A transient torque damper (not shown) may also be implemented betweenthe engine 12 and the input member 17 of the transmission.

In the embodiment depicted the engine 12 may be a fossil fuel engine,such as a diesel engine which is readily adapted to provide itsavailable power output typically delivered at a constant number ofrevolutions per minute (RPM).

Irrespective of the means by which the engine 12 is connected to thetransmission input member 17, the transmission input member 17 isoperatively connectable to planetary gear members in the transmission14.

An output member 19 of the transmission 14 is connected to a final drive16.

The transmission 14 utilizes two differential gear sets, preferably inthe nature of planetary gear sets 20 and 30. The planetary gear set 20employs an outer gear member 24, typically designated as the ring gearmember. The ring gear member 24 circumscribes an inner gear member 22,typically designated as the sun gear member. A carrier member 26rotatably supports a plurality of planet gears 27 such that each planetgear 27 meshingly engages both the outer, ring gear member 24 and theinner, sun gear member 22 of the first planetary gear set 20.

The planetary gear set 30 also has an outer gear member 34, often alsodesignated as the ring gear member that circumscribes an inner gearmember 32, also often designated as the sun gear member. A plurality ofplanet gears 37 are also rotatably mounted in a carrier member 36 suchthat each planet gear member 37 simultaneously, and meshingly, engagesboth the outer, ring gear member 34 and the inner, sun gear member 32 ofthe planetary gear set 30.

The output member 19 is secured to the ring gear member 34 of theplanetary gear set 30.

An interconnecting member 70 continuously connects the carrier member 26of the planetary gear set 20 with the carrier member 36 of the planetarygear set 30 and the transmission housing 60.

The first preferred embodiment 10 also incorporates first and secondmotor/generators 80 and 82, respectively. The stator of the firstmotor/generator 80 is secured to the transmission housing 60. The rotorof the first motor/generator 80 is secured to the sun gear member 22 ofthe planetary gear set 20.

The stator of the second motor/generator 82 is also secured to thetransmission housing 60. The rotor of the second motor/generator 82 issecured to the sun gear member 32 of the planetary gear set 30.

A first torque transfer device, such as an input clutch 50, selectivelyconnects the sun gear member 22 of the planetary gear set 20 with theinput shaft 17. A second torque transfer device, such as input clutch52, selectively connects the ring gear member 24 of the planetary gearset 20 with the input shaft 17. A third torque transfer device, such asclutch 54, selectively connects the ring gear member 34 of the planetarygear set 30 with the input shaft 17. The first, second and third torquetransfer devices 50, 52 and 54 are employed to assist in the selectionof the operational modes of the hybrid transmission 14, as will behereinafter more fully explained.

Returning now to the description of the power sources, it should beapparent from the foregoing description, and with particular referenceto FIG. 1 a, that the transmission 14 selectively receives power fromthe engine 12. The hybrid transmission also receives power from anelectric power source 86, which is operably connected to a controller88. The electric power source 86 may be one or more batteries. Otherelectric power sources, such as fuel cells, that have the ability toprovide, or store, and dispense electric power may be used in place ofbatteries without altering the concepts of the present invention.

General Operating Considerations

One of the primary control devices is a well known drive range selector(not shown) that directs an electronic control unit (the ECU 88) toconfigure the transmission for either the park, reverse, neutral, orforward drive range. The second and third primary control devicesconstitute an accelerator pedal (not shown) and a brake pedal (also notshown). The information obtained by the ECU from these three primarycontrol sources is designated as the “operator demand.” The ECU alsoobtains information from a plurality of sensors (input as well asoutput) as to the status of: the torque transfer devices (either appliedor released); the engine output torque; the unified battery, orbatteries, capacity level; and, the temperatures of selected vehicularcomponents. The ECU determines what is required and then manipulates theselectively operated components of, or associated with, the transmissionappropriately to respond to the operator demand.

The invention may use simple or compound planetary gear sets. In asimple planetary gear set a single set of planet gears are normallysupported for rotation on a carrier that is itself rotatable.

In a simple planetary gear set, when the sun gear is held stationary andpower is applied to the ring gear of a simple planetary gear set, theplanet gears rotate in response to the power applied to the ring gearand thus “walk” circumferentially about the fixed sun gear to effectrotation of the carrier in the same direction as the direction in whichthe ring gear is being rotated.

When any two members of a simple planetary gear set rotate in the samedirection and at the same speed, the third member is forced to turn atthe same speed, and in the same direction. For example, when the sungear and the ring gear rotate in the same direction, and at the samespeed, the planet gears do not rotate about their own axes but ratheract as wedges to lock the entire unit together to effect what is knownas direct drive. That is, the carrier rotates with the sun and ringgears.

However, when the two gear members rotate in the same direction, but atdifferent speeds, the direction in which the third gear member rotatesmay often be determined simply by visual analysis, but in manysituations the direction will not be obvious and can only be accuratelydetermined by knowing the number of teeth present on all the gearmembers of the planetary gear set.

Whenever the carrier is restrained from spinning freely, and power isapplied to either the sun gear or the ring gear, the planet gear membersact as idlers. In that way the driven member is rotated in the oppositedirection as the drive member. Thus, in many transmission arrangementswhen the reverse drive range is selected, a torque transfer deviceserving as a brake is actuated frictionally to engage the carrier andthereby restrain it against rotation so that power applied to the sungear will turn the ring gear in the opposite direction. Thus, if thering gear is operatively connected to the drive wheels of a vehicle,such an arrangement is capable of reversing the rotational direction ofthe drive wheels, and thereby reversing the direction of the vehicleitself.

In a simple set of planetary gears, if any two rotational speeds of thesun gear, the carrier member, and the--ring gear are known, then thespeed of the third member can be determined using a simple rule. Therotational speed of the carrier is always proportional to the speeds ofthe sun and the ring, weighted by their respective numbers of teeth. Forexample, a ring gear may have twice as many teeth as the sun gear in thesame set. The speed of the carrier is then the sum of two-thirds thespeed of the ring gear and one-third the speed of the sun gear. If oneof these three members rotates in an opposite direction, the arithmeticsign is negative for the speed of that member in mathematicalcalculations.

The torque on the sun gear, the carrier, and the ring gear can also besimply related to one another if this is done without consideration ofthe masses of the gears, the acceleration of the gears, or frictionwithin the gear set, all of which have a relatively minor influence in awell designed transmission. The torque applied to the sun gear of asimple planetary gear set must balance the torque applied to the ringgear, in proportion to the number of teeth on each of these gears. Forexample, the torque applied to a ring gear with twice as many teeth asthe sun gear in that set must be twice that applied to the sun gear, andmust be applied in the same direction. The torque applied to the carriermust be equal in magnitude and opposite in direction to the sum of thetorque on the sun gear and the torque on the ring gear.

In a compound planetary gear set, the utilization of inner and outersets of planet gears effects an exchange in the roles of the ring gearand the carrier member in comparison to a simple planetary gear set. Forinstance, if the sun gear is held stationary, the carrier member willrotate in the same direction as the ring gear, but the carrier memberwith inner and outer sets of planet gears will travel faster than thering gear, rather than slower.

In a compound planetary gear set having meshing inner and outer sets ofplanet gears the speed of the ring gear is proportional to the speeds ofthe sun gear and the carrier member, weighted by the number of teeth onthe sun gear and the number of teeth filled by the planet gears,respectively. For example, the difference between the ring and the sunfilled by the planet gears might be as many teeth as are on the sun gearin the same set. In that situation the speed of the ring gear would bethe sum of two-thirds the speed of the carrier and one third the speedof the sun. If the sun gear or the carrier member rotates in an oppositedirection, the arithmetic sign is negative for that speed inmathematical calculations.

If the sun gear were to be held stationary, then a carrier with innerand outer sets of planet gears will turn in the same direction as therotating ring gear of that set. On the other hand, if the sun gear wereto be held stationary and the carrier were to be driven, then planetgears in the inner set that engage the sun gear roll, or “walk,” alongthe sun gear, turning in the same direction that the carrier isrotating. Pinion gears in the outer set that mesh with pinion gears inthe inner set will turn in the opposite direction, thus forcing ameshing ring gear in the opposite direction, but only with respect tothe planet gears with which the ring gear is meshingly engaged. Theplanet gears in the outer set are being carried along in the directionof the carrier. The effect of the rotation of the pinion gears in theouter set on their own axis and the greater effect of the orbital motionof the planet gears in the outer set due to the motion of the carrierare combined, so the ring rotates in the same direction as the carrier,but not as fast as the carrier.

If the carrier in such a compound planetary gear set were to be heldstationary and the sun gear were to be rotated, then the ring gear willrotate with less speed and in the same direction as the sun gear. If thering gear of a simple planetary gear set is held stationary and the sungear is rotated, then the carrier supporting a single set of planetgears will rotate with less speed and in the same direction as the sungear. Thus, one can readily observe the exchange in roles between thecarrier and the ring gear that is caused by the use of inner and outersets of planet gears which mesh with one another, in comparison with theusage of a single set of planet gears in a simple planetary gear set.

The normal action of an electrically variable transmission is totransmit mechanical power from the input to the output. As part of thistransmission action, one of its two motor/generators acts as a generatorof electrical power. The other motor/generator acts as a motor and usesthat electrical power. As the speed of the output increases from zero toa high speed, the two motor/generators 80, 82 gradually exchange rolesas generator and motor, and may do so more than once. These exchangestake place around mechanical points, where essentially all of the powerfrom input to output is transmitted mechanically and no substantialpower is transmitted electrically.

In a hybrid electrically variable transmission system, the battery 86may also supply power to the transmission or the transmission may supplypower to the battery. If the battery is supplying substantial electricpower to the transmission, such as for vehicle acceleration, then bothmotor/generators may act as motors. If the transmission is supplyingelectric power to the battery, such as for regenerative braking, bothmotor/generators may act as generators. Very near the mechanical pointsof operation, both motor/generators may also act as generators withsmall electrical power outputs, because of the electrical losses in thesystem.

Contrary to the normal action of the transmission, the transmission mayactually be used to transmit mechanical power from the output to theinput. This may be done in a vehicle to supplement the vehicle brakesand to enhance or to supplement regenerative braking of the vehicle,especially on long downward grades. If the power flow through thetransmission is reversed in this way, the roles of the motor/generatorswill then be reversed from those in normal action.

Specific Operating Considerations

Each of the embodiments described herein has at least thirteenfunctional requirements (corresponding with the 13 or 14 rows of eachoperating mode table shown in the Figures) which may be grouped intofive operating modes. These five operating modes are described below andmay be best understood by referring to the respective operating modetable accompanying each transmission stick diagram, such as theoperating mode tables of FIGS. 1 b, 2 b, 3 b, etc.

The first operating mode is the “battery reverse mode” which correspondswith the first row (Batt Rev) of each operating mode table, such as thatof FIG. 1 b. In this mode, the engine is off and the transmissionelement connected to the engine is not controlled by engine torque,though there may be some residual torque due to the rotational inertiaof the engine. The EVT is driven by one of the motor/generators usingenergy from the battery, causing the vehicle to move in reverse.Depending on the kinematic configuration, the other/motor/generator mayor may not rotate in this mode, and may or may not transmit torque. Ifit does rotate, it is used to generate energy which is stored in thebattery. In the embodiment of FIG. 1 b, in the battery reverse mode, themotor/generator 80 has zero torque, and the motor 82 has 1.00 units oftorque. A torque ratio of −2.94 is achieved, by way of example. In eachoperating mode table an (M) next to a torque value in themotor/generator columns 80 and 82 indicates that the motor/generator isacting as a motor, and the absence of an (M) indicates that themotor/generator is acting as generator.

The second operating mode is the “EVT reverse mode” which correspondswith the second row (EVT Rev) of each operating mode table, such as thatof FIG. 1 b. In this mode, the EVT is driven by the engine and by one ofthe motor/generators. The other motor/generator operates in generatormode and transfers 100% of the generated energy back to the drivingmotor. The net effect is to drive the vehicle in reverse. Referring toFIG. 1 b, for example, in the EVT reverse mode, the clutch 52 isengaged, the generator 80 has a torque of 0.34 units, the motor 82 has atorque of 2.84 units, and an output torque of −8.33 is achieved,corresponding to an engine torque of 1 unit.

The third operating mode includes the “reverse and forward launch modes”(also referred to as “torque converter reverse and forward modes”)corresponding with the third and fourth rows (TC Rev and TC For) of eachoperating mode table, such as that of FIG. 1 b. In this mode, the EVT isdriven by the engine and one of the motor/generators. A selectablefraction of the energy generated in the generator unit is stored in thebattery, with the remaining energy being transferred to the motor. InFIG. 1, this fraction is approximately 99%. The ratio of transmissionoutput speed to engine speed (transmission speed ratio) is approximately+/−0.001 (the positive sign indicates that the vehicle is creepingforward and negative sign indicates that the vehicle is creepingbackwards). Referring to FIG. 1 b, in the reverse and forward launchmodes, the clutch 52 is engaged. In TC reverse, the motor/generator 80acts as a generator with 0.34 units of torque and the motor/generator 82acts as a motor with 2.38 units of torque, and a torque ratio of −7.00is achieved. In TC forward, the motor/generator 80 acts as a generatorwith 0.34 units of torque and the motor/generator 82 acts as a motorwith −1.60 units of torque, and a torque ratio of 4.69 is achieved.

The fourth operating mode is a “continuously variable transmission rangemode”. which includes the Range 1.1, Range 1.2, Range 1.3, Range 1.4,Range 1.5, Range 1.6, Range 1.7, and Range 1.8 operating pointscorresponding with rows 5-12 of each operating point table, such as thatof FIG. 1 b. In this mode, the EVT is driven by the engine as well asone of the motor/generators operating as a motor. The othermotor/generator operates as a generator and transfers 100% of thegenerated energy back to the motor. The operating points represented byRange 1.1, 1.2, . . . , etc. are discrete points in the continuum offorward speed ratios provided by the EVT. For example in FIG. 1 b, arange of torque ratios from 4.69 to 0.54 is achieved with the clutch 52engaged.

The fifth operating mode includes the “fixed ratio” mode (F1)corresponding with row 13 of each operating mode table (i.e. operatingmode table), such as that of FIG. 1 b. In this mode the transmissionoperates like a conventional automatic transmission, with two torquetransfer devices engaged to create a discrete transmission ratio. Theclutching table accompanying each figure shows one or two fixed-ratioforward speed but additional fixed ratios may be available. Referring toFIG. 1 b, in fixed ratio F1 the clutches 50 and 54 are engaged toachieve a fixed torque ratio of 1.00.

The transmission 14 is capable of operating in so-called single mode,only. In single mode, the engaged torque transfer device remains thesame for the entire continuum of forward speed ratios (represented bythe discrete points: Ranges 1.1, 1.2, 1.3 and 1.4).

As set forth above, the engagement schedule for the torque transferdevices is shown in the operating mode table and fixed ratio mode tableof FIG. 1 b. FIG. 1 b also provides an example of torque ratios that areavailable utilizing the ring gear/sun gear tooth ratios given by way ofexample in FIG. 1 b. The N_(R1)/N_(S1) value is the tooth ratio of theplanetary gear set 20 and the N_(R2)/NS₂ value is the tooth ratio of theplanetary gear set 30.

DESCRIPTION OF A SECOND EXEMPLARY EMBODIMENT

With reference to FIG. 2 a, a powertrain 110 is shown, including anengine 12 connected to one preferred embodiment of the improvedelectrically variable transmission, designated generally by the numeral114. Transmission 114 is designed to receive at least a portion of itsdriving power from the engine 12.

In the embodiment depicted the engine 12 may also be a fossil fuelengine, such as a diesel engine which is readily adapted to provide itsavailable power output typically delivered at a constant number ofrevolutions per minute (RPM). As shown, the engine 12 has an outputshaft that serves as the input member 17 of the transmission 114. Atransient torque damper (not shown) may also be implemented between theengine 12 and the input member 17 of the transmission.

Irrespective of the means by which the engine 12 is connected to thetransmission input member 17, the transmission input member 17 isoperatively connectable to planetary gear members in the transmission114. An output member 19 of the transmission 114 is connected to a fmaldrive 16.

The transmission 114 utilizes two differential gear sets, preferably inthe nature of planetary gear sets 120 and 130. The planetary gear set120 employs an outer gear member 124, typically designated as the ringgear member. The ring gear member 124 circumscribes an inner gear member122, typically designated as the sun gear member. A carrier member 126rotatably supports a plurality of planet gears 127 such that each planetgear 127 simultaneously, and meshingly engages both the outer, ring gearmember 124 and the inner, sun gear member 122 of the first planetarygear set 120.

The planetary gear set 130 also has an outer gear member 134, often alsodesignated as the ring gear member that circumscribes an inner gearmember 132, also often designated as the sun gear member. A plurality ofplanet gears 137 are also rotatably mounted in a carrier member 136 suchthat each planet gear member 137 simultaneously, and meshingly, engagesboth the outer, ring gear member 134 and the inner, sun gear member 132of the planetary gear set 130.

The transmission input member 17 is not continuously connected with anyplanetary gear member, and the transmission output member 19 isconnected with the carrier member 136 of the planetary gear set 130.

The transmission 114 also incorporates first and second motor/generators180 and 182, respectively. The stator of the first motor/generator 180is secured to the transmission housing 160. The rotor of the firstmotor/generator 180 is secured to the ring gear member 124 of theplanetary gear set 120.

The stator of the second motor/generator 182 is also secured to thetransmission housing 160. The rotor of the second motor/generator 182 issecured to the ring gear member 134 of the planetary gear set 130.

A first torque transfer device, such as input clutch 150, selectivelyconnects the ring gear member 124 of the planetary gear set 120 to theinput shaft 17. A second torque transfer device, such as input clutch152, selectively connects the carrier member 126 of the planetary gearset 120 with the input shaft 17. A third torque transfer device, such asclutch 154, selectively connects the ring gear member 124 of theplanetary gear set 120 with the carrier member 136 of the planetary gearset 30. The first, second and third torque transfer devices 150, 152 and154 are employed to assist in the selection of the operational modes ofthe hybrid transmission 114.

An interconnecting member 170 continuously connects transmission housing160 with the sun gear member 122 of the planetary gear set 120 and withthe sun gear member 132 of the planetary gear set 130.

Returning now to the description of the power sources, it should beapparent from the foregoing description, and with particular referenceto FIG 2 a, that the transmission 114 selectively receives power fromthe engine 12. The hybrid transmission also exchanges power with anelectric power source 186, which is operably connected to a controller188. The electric power source 186 may be one or more batteries. Otherelectric power sources, such as fuel cells, that have the ability toprovide, or store, and dispense electric power may be used in place ofbatteries without altering the concepts of the present invention.

As described previously, each embodiment has at least thirteenfunctional requirements (corresponding with the 13 or 14 rows of eachoperating mode table shown in the Figures) which may be grouped intofive operating modes. The first operating mode is the “battery reversemode” which corresponds with the first row (Batt Rev) of the operatingmode table of FIG. 2 b. In this mode, the engine is off and thetransmission element connected to the engine is effectively allowed tofreewheel, subject to engine inertia torque. The EVT is driven by one ofthe motor/generators using energy from the battery, causing the vehicleto move in reverse. The other motor/generator may or may not rotate inthis mode. As shown in FIG. 2 b, the motor/generator 180 has zerotorque, the motor 182 has a torque of −1.00 units and an output torqueof −1.33 is achieved, by way of example.

The second operating mode is the “EVT reverse mode” which correspondswith the second row (EVT Rev) of the operating mode table of FIG. 2 b.In this mode, the EVT is driven by the engine and by one of themotor/generators. The other motor/generator operates in generator modeand transfers 100% of the generated energy back to the driving motor.The net effect is to drive the vehicle in reverse. In this mode, theclutch 152 is engaged, the generator 180 has a torque of −0.75 units,the motor 182 has a torque of −6.25 units, and an output torque of −8.33is achieved, corresponding to an input torque of 1 unit.

The third operating mode includes the “reverse and forward launch modes”corresponding with the third and fourth rows (TC Rev and TC For) of eachoperating mode table, such as that of FIG. 2 b. In this mode, the EVT isdriven by the engine and one of the motor/generators. A selectablefraction of the energy generated in the generator unit is stored in thebattery, with the remaining energy being transferred to the motor. Inthis mode, the clutch 152 is engaged, and the motor/generator 180 actsas a generator in TC reverse with −0.75 units of torque and themotor/generator acts as a motor with −0.01 units of torque. In TCforward, the motor/generator 180 acts as a generator with −0.75 units oftorque, and the motor/generator 182 acts as a motor with 0.01 units oftorque. A torque ratio of −7.00 (TC reverse) or 4.69 (TC forward) isachieved. For these torque ratios, approximately 99% of the generatorenergy is stored in the battery.

The fourth operating mode includes the “Range 1.1, Range 1.2, Range 1.3,Range 1.4, Range 1.5, Range 1.6, Range 1.7 and Range 1.8” modescorresponding with rows 5-12 of the operating mode table of FIG. 2 b. Inthis mode, the EVT is driven by the engine as well as one of themotor/generators operating as a motor. The other motor/generatoroperates as a generator and transfers 100% of the generated energy backto the motor. The operating points represented by Range 1.1, 1.2, . . ., etc. are discrete points in the continuum of forward speed ratiosprovided by the EVT. For example in FIG. 2 b, a range of ratios from4.69 to 0.054 is achieved when the clutch 152 is engaged.

The fifth operating mode includes the fixed “ratio” modes (F1 and F2)corresponding with rows 13-14 of the operating mode table of FIG. 2 b.In this mode the transmission operates like a conventional automatictransmission, with two torque transfer devices engaged to create adiscrete transmission ratio. In fixed ratio F1 the clutches 150 and 154are engaged to achieve a fixed ratio of 1.00. In fixed ratio F2, theclutches 152 and 154 are engaged to achieve a fixed ratio of 0.75.

As set forth above, the engagement schedule for the torque transferdevices is shown in the operating mode table and fixed ratio mode tableof FIG. 2 b. FIG. 2 b also provides an example of torque ratios that areavailable utilizing the ring gear/sun gear tooth ratios given by way ofexample in FIG. 2 b. The N_(R1)/N_(S1) value is the tooth ratio of theplanetary gear set 120 and the N_(R2)/N_(S2) value is the tooth ratio ofthe planetary gear set 130. Also, the chart of FIG. 2 b describes theratio steps that are attained utilizing, the sample of tooth ratiosgiven. For example, the step ratio between first and second fixedforward torque ratios is 1.33.

DESCRIPTION OF A THIRD EXEMPLARY EMBODIMENT

With reference to FIG. 3 a, a powertrain 210 is shown, including anengine 12 connected to one preferred embodiment of the improvedelectrically variable transmission, designated generally by the numeral214. The transmission 214 is designed to receive at least a portion ofits driving power from the engine 12. As shown, the engine 12 has anoutput shaft that serves as the input member 17 of the transmission 214.A transient torque damper (not shown) may also be implemented betweenthe engine 12 and the input member 17 of the transmission 214.

Irrespective of the means by which the engine 12 is connected to thetransmission input member 17, the transmission input member isoperatively connectable to planetary gear members in the transmission214. An output member 19 of the transmission 214 is connected to a finaldrive 16.

The transmission 214 utilizes two differential gear sets, preferably inthe nature of planetary gear sets 220 and 230. The planetary gear set220 employs an outer gear member 224, typically designated as the ringgear member. The ring gear member 224 circumscribes an inner gear member222, typically designated as the sun gear member. A carrier member 226rotatably supports a plurality of planet gears 227 such that each planetgear 227 simultaneously, and meshingly engages both the inner, sun gearmember 222, and the outer, ring gear member 224 of the first planetarygear set 220.

The planetary gear set 230 also has an outer ring gear member 234 thatcircumscribes an inner sun gear member 232. A carrier member 236rotatably supports a plurality of planet gears 237, 238 such that eachplanet gear 238 meshingly engages the sun gear member 232, and eachplanet gear 237 meshingly engages the ring gear member 234 and therespective planet gear 238.

The transmission input member 17 is not continuously connected with anyplanetary gear member, and the transmission output member 19 isconnected to the ring gear member 234 of the planetary gear set 230.

An interconnecting member 270 continuously connects the carrier member226 of the planetary gear set 220 with the sun gear member 232 of theplanetary gear set 230 and the transmission housing 260.

The transmission 214 also incorporates first and second motor/generators280 and 282, respectively. The stator of the first motor/generator 280is secured to the transmission housing 260. The rotor of the firstmotor/generator 280 is secured to the sun gear member 222 of theplanetary gear set 220.

The stator of the second motor/generator 282 is also secured to thetransmission housing 260. The rotor of the second motor/generator 282 issecured to the carrier member 236 of the planetary gear set 230.

A first torque-transfer device, such as input clutch 250, selectivelyconnects the ring gear member 224 of the planetary gear set 220 with theinput shaft 17. A second torque-transfer device, such as input clutch252, selectively connects the carrier member 236 of the planetary gearset 230 with the input shaft 17. A third torque-transfer device, such asa clutch 254, selectively connects the ring gear member 224 of theplanetary gear set 220 with the carrier member 236 of the planetary gearset 230. The first, second and third torque-transfer devices 250, 252and 254 are employed to assist-in the selection of the operational modesof the hybrid transmission 214.

The hybrid transmission 214 receives power from the engine 12, and alsofrom electric power source 286, which is operably connected to acontroller 288.

The operating mode table of FIG. 3 b illustrates the clutchingengagements, motor/generator conditions and output/input ratios for thefive operating modes of the transmission 214. These modes include the“battery reverse mode” (Batt Rev), “EVT reverse mode” (EVT Rev),“reverse and forward launch modes” (TC Rev and TC For), “range 1.1, 1.2,1.3 . . . modes” and “fixed ratio mode” (F1) as described previously.

As set forth above the engagement schedule for the torque-transferdevices is shown in the operating mode table and fixed ratio mode tableof FIG. 3 b. FIG. 3 b also provides an example of torque ratios that areavailable utilizing the ring gear/sun gear tooth ratios given by way ofexample in FIG. 3 b. The N_(R1)/N_(S1) value is the tooth ratio of theplanetary gear set 220 and the N_(R2)/N_(S2) value is the tooth ratio ofthe planetary gear set 230.

DESCRIPTION OF A FOURTH EXEMPLARY EMBODIMENT

With reference to FIG. 4 a, a powertrain 310 is shown, including anengine 12 connected to one preferred embodiment of the improvedelectrically variable transmission, designated generally by the numeral314. The transmission 314 is designed to receive at least a portion ofits driving power from the engine 12.

As shown, the engine 12 has an output shaft that serves as the inputmember 17 of the transmission 314. A transient torque damper (not shown)may also be implemented between the engine 12 and the input member 17 ofthe transmission.

Irrespective of the means by which the engine 12 is connected to thetransmission input member 17, the transmission input member 17 isoperatively connectable to planetary gear members in the transmission314. An output member 19 of the transmission 314 is connected to a finaldrive 16.

The transmission 314 utilizes two planetary gear sets 320 and 330. Theplanetary gear set 320 employs an outer ring gear member 324 whichcircumscribes an inner sun gear member 322. A carrier member 326rotatably supports a plurality of planet gears 327 such that each planetgear 327 simultaneously, and meshingly engages both the inner sun gearmember 322, and the outer ring gear member 324.

The planetary gear set 330 also has an outer ring gear member 334 thatcircumscribes an inner sun gear member 332. A plurality of planet gears337 are also rotatably mounted in a carrier member 336 such that eachplanet gear member 337 simultaneously, and meshingly engages both theinner, sun gear member 332, and the outer, ring gear member 334.

The transmission input member 17 is not continuously connected with anyplanetary gear member, and the transmission output member 19 isconnected with the carrier member 336 of the planetary gear set 330.

An interconnecting member 370 continuously connects the carrier member326 of the planetary gear set 320 with the sun gear member 332 of theplanetary gear set 330 and the transmission housing 360.

The transmission 314 also incorporates first and second motor/generators380 and 382, respectively. The stator of the first motor/generator 380is secured to the transmission housing 360. The rotor of the firstmotor/generator 380 is secured to the sun gear member 322 of theplanetary gear set 320. The stator of the second motor/generator 382 isalso secured to the transmission housing 360. The rotor of the secondmotor/generator 382 is secured to the ring gear member 334 of theplanetary gear set 330.

A first torque-transfer device, such as the input clutch 350,selectively connects the ring gear member 324 with the input shaft 17. Asecond torque-transfer device, such as the input clutch 352, selectivelyconnects the ring gear member 334 with the input shaft 17. A thirdtorque-transfer device, such as clutch 354, selectively connects thering gear member 324 with the ring gear member 334. The first, secondand third torque-transfer devices 350, 352 and 354 are employed toassist in the selection of the operational modes of the transmission314.

The hybrid transmission 314 receives power from the engine 12, and alsoexchanges power with an electric power source 386, which is operablyconnected to a controller 388.

The operating mode table of FIG. 4 b illustrates the clutchingengagements, motor/generator conditions and output/input ratios for thefive operating modes of the transmission 314. These modes include the“battery reverse mode” (Batt Rev), the “EVT reverse mode” (EVT Rev),“reverse and forward launch modes” (TC Rev and TC For), “continuouslyvariable transmission range modes” (Range 1.1, 1.2, 1.3 . . . ) and“fixed ratio mode” (F1) as described previously.

As set forth above, the engagement schedule for the torque-transferdevices is shown in the operating mode table and fixed ratio mode tableof FIG. 4 b. FIG. 4 b also provides an example of torque ratios that areavailable utilizing the ring gear/sun gear tooth ratios given by way ofexample in FIG. 4 b. The N_(R1)/N_(S1) value is the tooth ratio of theplanetary gear set 320 and the N_(R2)/N_(S2) value is the tooth ratio ofthe planetary gear set 330.

DESCRIPTION OF A FIFTH EXEMPLARY EMBODIMENT

With reference to FIG. 5 a, a powertrain 410 is shown, including anengine 12 connected to one preferred embodiment of the improvedelectrically variable transmission, designated generally by the numeral414. The transmission 414 is designed to receive at least a portion ofits driving power from the engine 12.

As shown, the engine 12 has an output shaft that serves as the inputmember 17 of the transmission 414. A transient torque damper (not shown)may also be implemented between the engine 12 and the input member 17 ofthe transmission.

Irrespective of the means by which the engine 12 is connected to thetransmission input member 17, the transmission input member 17 isoperatively connectable to planetary gear members in the transmission414. An output member 19 of the transmission 414 is connected to a finaldrive 16.

The transmission 414 utilizes two planetary gear sets 420 and 430. Theplanetary gear set 420 employs an outer ring gear member 424 whichcircumscribes an inner sun gear member 422. A carrier member 426rotatably supports a plurality of planet gears 427 such that each planetgear 427 meshingly engages both the outer ring gear member 424 and theinner sun gear member 422 of the first planetary gear set 420.

The planetary gear set 430 also has an outer ring gear member 434 thatcircumscribes an inner sun gear member 432. A plurality of planet gears437 are also rotatably mounted in a carrier member 436 such that eachplanet gear member 437 simultaneously, and meshingly engages both theouter, ring gear member 434 and the inner, sun gear member 432 of theplanetary gear set 430.

The transmission input member 17 is not continuously connected with anyplanetary gear member, and the transmission output member 19 iscontinuously connected with the ring gear member 434.

An interconnecting member 470 continuously connects the ring gear member424 of the planetary gear set 420 with the carrier member 436 of theplanetary gear set 430 and with the transmission housing 460.

The transmission 414 also incorporates first and second motor/generators480 and 482, respectively. The stator of the first motor/generator 480is secured to the transmission housing 460. The rotor of the firstmotor/generator 480 is secured to the sun gear member 422.

The stator of the second motor/generator 482 is also secured to thetransmission housing 460. The rotor of the second motor/generator 482 issecured to the sun gear member 432.

A first torque-transfer device, such as an input clutch 450, selectivelyconnects the carrier member 426 with the input shaft 17. A secondtorque-transfer device, such as input clutch 452, selectively connectsthe sun gear member 422 with the input shaft 17. A third torque-transferdevice, such as clutch 454, selectively connects the carrier member 426with the ring gear member 434. The first, second and thirdtorque-transfer devices 450, 452 and 454 are employed to assist in theselection of the operational modes of the transmission 414. The hybridtransmission 414 receives power from the engine 12 and also from anelectric power source 486, which is operably connected to a controller488.

The operating mode table of FIG. 5 b illustrates the clutchingengagements, motor/generator conditions and output/input ratios for thefive operating modes of the transmission 414. These modes include the“battery reverse mode” (Batt Rev), the “EVT reverse mode” (EVT Rev),“reverse and forward launch modes” (TC Rev and TC For), “continuouslyvariable transmission range modes” (Range 1.1, 1.2, 1.3 . . . ) and“fixed ratio mode” (F1) as described previously.

As set forth above, the engagement schedule for the torque-transferdevices is shown in the operating mode table and fixed ratio mode tableof FIG. 5 b. FIG. 5 b also provides an example of torque ratios that areavailable utilizing the ring gear/sun gear tooth ratios given by way ofexample in FIG. 5 b. The N_(R1)/N_(S1) value is the tooth ratio of theplanetary gear set 420 and the N_(R2)/N_(S2) value is the tooth ratio ofthe planetary gear set 430.

DESCRIPTION OF A SIXTH EXEMPLARY EMBODIMENT

With reference to FIG. 6 a, a powertrain 510 is shown, including anengine 12 connected to one preferred embodiment of the improvedelectrically variable transmission, designated generally by the numeral514. The transmission 514 is designed to receive at least a portion ofits driving power from the engine 12.

As shown, the engine 12 has an output shaft that serves as the inputmember 17 of the transmission 514. A transient torque damper (not shown)may also be implemented between the engine 12 and the input member 17 ofthe transmission.

Irrespective of the means by which the engine 12 is connected to thetransmission input member 17, the transmission input member 17 isoperatively connectable to planetary gear members in the transmission514. An output member 19 of the transmission 514 is connected to a finaldrive 16.

The transmission 514 utilizes two planetary gear sets 520 and 530. Theplanetary gear set 520 employs an outer ring gear member 524 whichcircumscribes an inner sun gear member 522. A carrier member 526rotatably supports a plurality of planet gears 527 such that each planetgear 527 simultaneously, and meshingly engages both the outer ring gearmember 524 the inner sun gear member 522.

The planetary gear set 530 also has an outer ring gear member 534 thatcircumscribes an inner sun gear member 532. A plurality of planet gears537 are also rotatably mounted in a carrier member 536 such that eachplanet gear member 537 simultaneously, and meshingly engages both theinner, sun gear member 532, and the outer, ring gear member 534 of theplanetary gear set 530.

The transmission input member 17 is not continuously connected with anyplanetary gear member, and the transmission output member 19 iscontinuously connected with the carrier member 536.

An interconnecting member 570 continuously connects the ring gear member524 of the planetary gear set 520 with the sun gear member 532 of theplanetary gear set 530 and with the transmission housing 560.

The transmission 514 also incorporates first and second motor/generators580 and 582, respectively. The stator of the first motor/generator 580is secured to the transmission housing 560. The rotor of the firstmotor/generator 580 is secured to the sun gear member 522.

The stator of the second motor/generator 582 is also secured to thetransmission housing 560. The rotor of the second motor/generator 582 issecured to the ring gear member 534.

A first torque-transfer device, such as input clutch 550, selectivelyconnects the sun gear member 522 with the input member 17. A secondtorque-transfer device, such as input clutch 552, selectively connectsthe carrier member 526 with the input member 17. A third torquetransmitting device, such as clutch 554, selectively connects thecarrier member 526 with the carrier member 536. The first, second andthird torque-transfer devices 550, 552 and 554 are employed to assist inthe selection of the operational modes of the hybrid transmission 514.

The hybrid transmission 514 receives power from the engine 12, and alsoexchanges power with an electric power source 586, which is operablyconnected to a controller 588.

The operating mode table of FIG. 6 b illustrates the clutchingengagements, motor/generator conditions and output/input ratios for thefive operating modes of the transmission 514. These modes include the“battery reverse mode” (Batt Rev), the “EVT reverse mode” (EVT Rev),“reverse and forward launch modes” (TC Rev and TC For), “continuouslyvariable transmission range modes” (Range 1.1, 1.2, 1.3 . . . ) and“fixed ratio modes” (F1, F2) as described previously.

As set forth above, the engagement schedule for the torque-transferdevices is shown in the operating mode table and fixed ratio mode tableof FIG. 6 b. FIG. 6 b also provides an example of torque ratios that areavailable utilizing the ring gear/sun gear tooth ratios given by way ofexample in FIG. 6 b. The N_(R1)/N_(S1) value is the tooth ratio of theplanetary gear set 520 and the N_(R2)/N_(S2) value is the tooth ratio ofthe planetary gear set 530. Also, the chart of FIG. 4 b describes theratio steps that are attained utilizing the sample of tooth ratiosgiven. For example, the step ratio between first and second fixedforward torque ratios is 2.51.

DESCRIPTION OF A SEVENTH EXEMPLARY EMBODIMENT

With reference to FIG. 7 a, a powertrain 610 is shown, including anengine 12 connected to one preferred embodiment of the improvedelectrically variable transmission, designated generally by the numeral614. The transmission 614 is designed to receive at least a portion ofits driving power from the engine 12.

As shown, the engine 12 has an output shaft that serves as the inputmember 17 of the transmission 614. A transient torque damper (not shown)may also be implemented between the engine 12 and the input member 17 ofthe transmission.

Irrespective of the means by which the engine 12 is connected to thetransmission input member 17, the transmission input member 17 isoperatively connectable to planetary gear members in the transmission614. An output member 19 of the transmission 614 is connected to a finaldrive 16.

The transmission 614 utilizes two planetary gear sets 620 and 630. Theplanetary gear set 620 employs an outer ring gear member 624 whichcircumscribes an inner sun gear member 622. A carrier member 626rotatably supports a plurality of planet gears 627 such that each planetgear 627 simultaneously, and meshingly engages both the outer ring gearmember 624 and the inner sun gear member 622.

The planetary gear set 630 also has an outer ring gear member 634 thatcircumscribes an inner sun gear member 632. A plurality of planet gears637 are also rotatably mounted in a carrier member 636 such that eachplanet gear member 637 simultaneously, and meshingly engages both theouter, ring gear member 634 and the inner, sun gear member 632 of theplanetary gear set 630.

The transmission input member 17 is not continuously connected with anyplanetary gear member, and the transmission output member 19 iscontinuously connected with the ring gear member 624.

An interconnecting member 670 continuously connects the carrier member626 of the planetary gear set 620 with the ring gear member 634 of theplanetary gear set 630 and with the transmission housing 660.

The transmission 614 also incorporates first and second motor/generators680 and 682, respectively. The stator of the first motor/generator 680is secured to the transmission housing 660. The rotor of the firstmotor/generator 680 is secured to the sun gear member 622.

The stator of the second motor/generator 682 is also secured with thetransmission housing 660. The rotor of the second motor/generator 682 issecured to the sun gear member 632.

A first torque-transfer device, such as input clutch 650, selectivelyconnects the ring gear member 624 with the input shaft 17. A secondtorque-transfer device, such as input clutch 652, selectively connectsthe carrier member 636 with the input shaft 17. The first and secondtorque-transfer devices 650 and 652 are employed to assist in theselection of the operational modes of the hybrid transmission 614.

The hybrid transmission 614 receives power from the engine 12, and alsoexchanges power with an electric power source 686, which is operablyconnected to a controller 688.

The operating mode table of FIG. 7 b illustrates the clutchingengagements, motor/generator conditions and output/input ratios for thefive operating modes of the transmission 614. These modes include the“battery reverse mode” (Batt Rev), the “EVT reverse mode” (EVT Rev),“reverse and forward launch modes” (TC Rev and TC For), “continuouslyvariable transmission range modes” (Range 1.1, 1.2, 1.3 . . . ) and“fixed ratio mode” (F1) as described previously.

As set forth above, the engagement schedule for the torque-transferdevices is shown in the operating mode table and fixed ratio mode tableof FIG. 7 b. FIG. 7 b also provides an example of torque ratios that areavailable utilizing the ring gear/sun gear tooth ratios given by way ofexample in FIG. 7 b. The N_(R1)/N_(S1) value is the tooth ratio of theplanetary gear set 620 and the N_(R2)/N_(S2) value is the tooth ratio ofthe planetary gear set 630.

DESCRIPTION OF AN EIGHTH EXEMPLARY EMBODIMENT

With reference to FIG. 8 a, a powertrain 710 is shown, including anengine 12 connected to one preferred embodiment of the improvedelectrically variable transmission, designated generally by the numeral714. The transmission 714 is designed to receive at least a portion ofits driving power from the engine 12.

As shown, the engine 12 has an output shaft that serves as the inputmember 17 of the transmission 714. A transient torque damper (not shown)may also be appointed between the engine 12 and the input member 17 ofthe transmission.

Irrespective of the means by which the engine 12 is connected to thetransmission input member 17, the transmission input member 17 isoperatively connectable to planetary gear members in the transmission714. An output member 19 of the transmission 714 is connected to a finaldrive 16.

The transmission 714 utilizes two planetary gear sets 720 and 730. Theplanetary gear set 720 employs an outer ring gear member 724 whichcircumscribes an inner sun gear member 722. A carrier member 726rotatably supports a plurality of planet gears 727 such that each planetgear 727 simultaneously, and meshingly engages both the outer ring gearmember 724 and the inner sun gear member 722.

The planetary gear set 730 also has an outer ring gear member 734 thatcircumscribes an inner sun gear member 732. A carrier member 736rotatably supports a plurality of planet gears 737 such that each planetgear 737 simultaneously, and meshingly engages the outer ring gearmember 734 and the inner sun gear member 732.

The transmission input member 17 is not continuously connected with anyplanetary gear member, and the transmission output member 19 iscontinuously connected with the carrier member 736.

An interconnecting member 770 continuously connects the ring gear member724 of the planetary gear set 720 with the ring gear member 734 of theplanetary gear set 730 and with the transmission housing 760.

The transmission 714 also incorporates first and second motor/generators780 and 782, respectively. The stator of the first motor/generator 780is secured to the transmission housing 760. The rotor of the firstmotor/generator 780 is secured to the sun gear member 722 of theplanetary gear set 720.

The stator of the second motor/generator 782 is also secured to thetransmission housing 760. The rotor of the second motor/generator 782 issecured to the sun gear member 732 of the planetary gear set 730.

A first torque-transfer device, such as input clutch 750, selectivelyconnects the sun gear member 722 with the input member 17. A secondtorque-transfer device, such as input clutch 752, selectively connectsthe carrier member 726 with the input member 17. A third torquetransmitting device, such as clutch 754, selectively connects sun gearmember 722 with the sun gear member 732. The first, second and thirdtorque-transfer devices 750, 752 and 754 are employed to assist in theselection of the operational modes of the hybrid transmission 714.

The hybrid transmission 714 receives power from the engine 12, and alsoexchanges power with an electric power source 786, which is operablyconnected to a controller 788.

The operating mode table of FIG. 8 b illustrates the clutchingengagements, motor/generator conditions and output/input ratios for thefive operating modes of the transmission 714. These modes include the“battery reverse mode” (Batt Rev), the “EVT reverse mode” (EVT Rev),“reverse and forward launch modes” (TC Rev and TC For), “continuouslyvariable transmission range modes” (Range 1.1, 1.2, 1.3 . . . ) and“fixed ratio modes” (F1 and F2) as described previously.

As set forth above, the engagement schedule for the torque-transferdevices is shown in the operating mode table and fixed ratio mode tableof FIG. 8 b. FIG. 8 b also provides an example of torque ratios that areavailable utilizing the ring gear/sun gear tooth ratios given by way ofexample in FIG. 8 b. The N_(R1)/N_(S1) value is the tooth ratio of theplanetary gear set 720 and the N_(R2)/N_(S2) value is the tooth ratio ofthe planetary gear set 730.

DESCRIPTION OF A NINTH EXEMPLARY EMBODIMENT

With reference to FIG. 9 a, a powertrain 810 is shown, including anengine 12 connected to one preferred embodiment of the improvedelectrically variable transmission, designated generally by the numeral814. The transmission 814 is designed to receive at least a portion ofits driving power from the engine 12.

As shown, the engine 12 has an output shaft that serves as the inputmember 17 of the transmission 814. A transient torque damper (not shown)may also be implemented between the engine 12 and the input member 17 ofthe transmission.

Irrespective of the means by which the engine 12 is connected to thetransmission input member 17, the transmission input member 17 isoperatively connectable to planetary gear members in the transmission814. An output member 19 of the transmission 814 is connected to a finaldrive 16.

The transmission 814 utilizes two planetary gear sets 820 and 830. Theplanetary gear set 820 employs an outer ring gear member 824 whichcircumscribes an inner sun gear member 822. A carrier member 826rotatably supports a plurality of planet gears 827 such that each planetgear 827 simultaneously, and meshingly engages both the outer ring gearmember 824 and the inner sun gear member 822 of the first planetary gearset 820.

The planetary gear set 830 also has an outer ring gear member 834 thatcircumscribes an inner sun gear member 832. A plurality of planet gears837 are also rotatably mounted in a carrier member 836 such that eachplanet gear member 837 simultaneously, and meshingly engages both theouter, ring gear member 834 and the inner, sun gear member 832 of theplanetary gear set 830.

The transmission input member 17 is not continuously connected with anyplanetary gear member, and the transmission output member 19 iscontinuously connected with the carrier member 826.

An interconnecting member 870 continuously connects the ring gear member824 of the planetary gear set 820 with the sun gear member 832 of theplanetary gear set 830 and with the transmission housing 860.

The transmission 814 also incorporates first and second motor/generators880 and 882, respectively. The stator of the first motor/generator 880is secured to the transmission housing 860. The rotor of the firstmotor/generator 880 is secured to the sun gear member 822.

The stator of the second motor/generator 882 is also secured to thetransmission housing 860. The rotor of the second motor/generator 882 issecured to the ring gear member 834.

A first torque-transfer device, such as input clutch 850, selectivelyconnects the sun gear member 822 with the input shaft 17. A secondtorque-transfer device, such as input clutch 852, selectively connectsthe carrier member 836 with the input shaft 17. A third torque-transferdevice, such as clutch 854, selectively connects the carrier member 826with the carrier member 836. The first, second and third torque-transferdevices 850, 852 and 854 are employed to assist in the selection of theoperational modes of the hybrid transmission 814.

The hybrid transmission 814 receives power from the engine 12, andexchanges power with an electric power source 886, which is operablyconnected to a controller 888.

The operating mode table of FIG. 9 b illustrates the clutchingengagements, motor/generator conditions and output/input ratios for thefive operating modes of the transmission 814. These modes include the“battery reverse mode” (Batt Rev), the “EVT reverse mode” (EVT Rev),“reverse and forward launch modes” (TC Rev and TC For), “continuouslyvariable transmission range modes” (Range 1.1, 1.2, 1.3 . . . ) and“fixed ratio modes” (F1 and F2) as described previously.

As set forth above, the engagement schedule for the torque-transferdevices is shown in the operating mode table and fixed ratio mode tableof FIG. 9 b. FIG. 9 b also provides an example of torque ratios that areavailable utilizing the ring gear/sun gear tooth ratios given by way ofexample in FIG. 9 b. The N_(R1)/N_(S1) value is the tooth ratio of theplanetary gear set 820 and the N_(R2)/N_(S2) value is the tooth ratio ofthe planetary gear set 830. Also, the chart of FIG. 9 b describes theratio steps that are attained utilizing the sample of tooth ratiosgiven. For example, the step ratio between first and second fixedforward torque ratios is 2.51.

In the claims, the language “continuously connected” or “continuouslyconnecting” refers to a direct connection or a proportionally gearedconnection, such as gearing to an offset axis. Also, the “stationarymember” or “ground” may include the transmission housing (case) or anyother non-rotating component or components. Also, when a torquetransmitting mechanism is said to connect something to a member of agear set, it may also be connected to an interconnecting member whichconnects it with that member.

While various preferred embodiments of the present invention aredisclosed, it is to be understood that the concepts of the presentinvention are susceptible to numerous changes apparent to one skilled inthe art. Therefore, the scope of the present invention is not to belimited to the details shown and described but is intended to includeall variations and modifications which come within the scope of theappended claims.

1. An electrically variable transmission comprising: an input member toreceive power from an engine; an output member; first and secondmotor/generators; first and second differential gear sets each havingfirst, second and third members; said input member not beingcontinuously connected with any member of said gear sets, and saidoutput member being continuously connected with a member of said gearsets; an interconnecting member continuously connecting said firstmember of said first gear set with said first member of said second gearset and with a stationary member; said first motor/generator beingcontinuously connected with a member of said first gear set; said secondmotor/generator being continuously connected with a member of saidsecond gear set; a first torque transfer device selectively connectingsaid input member with a member of said first gear set; a second torquetransfer device selectively connecting said input member with a memberof said first or second gear set, this member being different from theone connected by said first torque transfer device; and wherein saidfirst and second torque transfer devices are engageable singly or inpairs to provide an electrically variable transmission with acontinuously variable range of speed ratios and at least one fixedforward speed ratio.
 2. The electrically variable transmission of claim1, wherein said first and second differential gear sets are planetarygear sets, each including a ring gear, a sun gear and a carrier.
 3. Theelectrically variable transmission of claim 2, wherein carriers of eachof said planetary gear sets are single-pinion carriers.
 4. Theelectrically variable transmission of claim 2, wherein at least onecarrier of said planetary gear sets is a double-pinion carrier.
 5. Theelectrically variable transmission of claim 2, wherein said first andsecond torque transfer devices and said first and secondmotor/generators are operable to provide five operating modes in theelectrically variable transmission, including battery reverse mode, EVTreverse mode, reverse and forward launch modes, continuously variabletransmission range mode, and fixed ratio mode.
 6. The electricallyvariable transmission of claim 1, further comprising a third torquetransfer device selectively connecting a member of said second planetarygear set with said input member or with a member of said first planetarygear set.
 7. An electrically variable transmission comprising: an inputmember to receive power from an engine; an output member; first andsecond motor/generators; first and second differential gear sets eachhaving first, second and third members; said input member not beingcontinuously connected with any member of said gear sets, and saidoutput member being continuously connected with a member of said gearsets; an interconnecting member continuously connecting said firstmember of said first gear set with said first member of said second gearset and with a stationary member; said first motor/generator beingcontinuously connected with a member of said first gear set; said secondmotor/generator being continuously connected with a member of saidsecond gear set; and first, second and third torque transfer devices forselectively connecting said members of said first or second gear setswith said input member or with other members of said gear sets, saidfirst, second and third torque transfer devices being engageable toprovide an electrically variable transmission with a continuouslyvariable range of speed ratios and at least one fixed forward speedratio between said input member and said output member.
 8. Theelectrically variable transmission of claim 7, wherein said first andsecond differential gear sets are planetary gear sets, and said firsttorque transfer device selectively connects said input member with amember of said first planetary gear set.
 9. The electrically variabletransmission of claim 8, wherein said second torque transfer deviceselectively connects said input member with a member of said first orsecond planetary gear set.
 10. The electrically variable transmission ofclaim 9, wherein said third torque transfer device selectively connectssaid input member with a member of said second planetary gear set. 11.The electrically variable transmission of claim 9, wherein said thirdtorque transfer device selectively connects a member of said secondplanetary gear set with a member of said first planetary gear set. 12.The electrically variable transmission of claim 7, wherein carriers ofeach of said planetary gear sets are single-pinion carriers.
 13. Theelectrically variable transmission of claim 7, wherein at least onecarrier of said planetary gear sets is a double-pinion carrier.
 14. Anelectrically variable transmission comprising: an input member toreceive power from an engine; an output member; first and secondmotor/generators; first and second differential gear sets each havingfirst, second and third members; said input member not beingcontinuously connected with any member of said gear sets, and saidoutput member being continuously connected with a member of said gearsets; an interconnecting member continuously connecting said firstmember of said first gear set with said first member of said second gearset and with a stationary member; said first motor/generator beingcontinuously connected with a member of said first gear set; said secondmotor/generator being continuously connected with a member of saidsecond gear set; a first torque transfer device selectively connectingsaid input member with a member of said first gear set; a second torquetransfer device selectively connecting said input member with a memberof said first or second gear set, this member being different from theone connected by said first torque transfer device; a third torquetransmitting device selectively connecting a member of said second gearset with said input member or with a member of said first gear set; andwherein said first and second torque transfer devices are engagablesingly or in pairs to provide an electrically variable transmission witha continuously variable range of speed ratios and at least one fixedforward speed ratio.